Patent Document 1 (JP 2009-222256A) discloses an ejector refrigeration cycle. In the refrigeration cycle, a branch portion for branching a flow of refrigerant flowing out of a radiator is provided upstream of an ejector that functions as a refrigerant depressurizing means and a refrigerant circulating means. One flow of refrigerant branched at the branch portion causes to flow into the nozzle portion of the ejector, and the other flow of refrigerant causes to flow toward the refrigerant suction port of the ejector.
In the conventional technology, a first evaporator is disposed downstream of the diffuser portion (pressurizing portion) of the ejector, and a throttling mechanism and a second evaporator are disposed between the branch portion and the refrigerant suction port of the ejector. Thus, the refrigeration capacity can be obtained in both the first and second evaporators.
In the conventional technology, a flow amount divider is arranged at the refrigerant branch portion. The flow amount divider carries out gas-liquid separation by the centrifugal force or gravity of refrigerant, so that the refrigerant is separated into gas and liquid and is divided to the nozzle portion side of the ejector and the side of the throttling mechanism and the second evaporator.
The dryness of refrigerant on the nozzle portion side of the ejector is thereby made lower than the dryness of refrigerant on the side of the throttling mechanism and the second evaporator. The efficiency (COP) of the refrigeration cycle is thereby enhanced.
In general, each ejector applied to ejector refrigeration cycles is formed in a substantially cylindrical shape. A refrigerant inflow port is provided at one end of the ejector in the longitudinal direction and a refrigerant outflow port is provided at the other end thereof in the longitudinal direction. In addition, a refrigerant suction port is provided in the cylinder wall surface between the refrigerant inflow port and the refrigerant outflow port.
In the ejector refrigeration cycle, therefore, it is necessary to connect other cycle component equipment to the refrigerant inflow port, the refrigerant outflow port, and the refrigerant suction port of the ejector. This complicates the connection with the other cycle component equipment as compared with ordinary refrigeration cycles (expansion valve cycles) not provided with an ejector.
In the ejector refrigeration cycle, for this reason, degradation in incorporability is incurred when it is incorporated in a product, such as an air conditioning system and a refrigeration unit, unlike ordinary refrigeration cycles. In consideration of the above, for example, Patent Documents 2 and 3 (JP 2007-57222A and JP 2007-192465A) propose that an ejector, first and second evaporators, and the like are integrated as an evaporator unit, so as to enhance the incorporability of the ejector refrigeration cycle in products.
The present inventors considered taking the following measure to enhance the incorporability of ejector refrigeration cycles: a gas-liquid separation portion and a refrigerant dividing portion equivalent to the flow amount divider in Patent Document 1 are integrated as an evaporator unit together with an ejector and first and second evaporators.
However, this involves a problem. To separate refrigerant into gas and liquid at the gas-liquid separation portion, a certain space is necessary. Therefore, when the gas-liquid separation portion and the refrigerant dividing portion are integrated as an evaporator unit together with the ejector and the first and second evaporators, the physical size of the evaporator unit is increased.
The gas-liquid separation portions used in refrigeration cycles are required that the gas-liquid separation of refrigerant should be stably carried out even when the refrigerant flow amount is varied by an air conditioning load.
In the evaporator units in Patent Documents 2 and 3, a first evaporator and a second evaporator are disposed in series with respect to the flow of air as the fluid to be cooled so that air sent to an identical space to be cooled can be cooled at both the evaporators.
However, in the evaporator unit disclosed in Patent Document 2, as viewed in the direction of air flow, the downstream area of the heat exchange core portion of the first evaporator in the refrigerant flow and the downstream area of the heat exchange core portion of the second evaporator in the refrigerant flow are overlapped with each other. As a result, a temperature distribution is produced in the air blown out of the evaporator unit.
The reason for this is as follows: in the downstream area of the heat exchange core portion of an evaporator in the refrigerant flow, the refrigerant is brought into gas phase and it has a degree of superheat. More specific description will be given. The air passing through the downstream areas (hereafter, referred to as superheat areas) of the heat exchange core portions of both the evaporators in the refrigerant flow only absorbs the sensible heat from the refrigerant. Therefore, the air is not sufficiently cooled, as compared with a case where the air absorbs evaporation latent heat. In the evaporator unit in Patent Document 2, as a result, a temperature distribution is produced in air blown out.
In the evaporator unit in Patent Document 3, in order to suppress the temperature distribution of air blown out of the evaporator unit, the evaporators are so arranged that the superheat area of the first evaporator and the superheat area of the second evaporator do not overlap with each other as viewed in the direction of air flow. As described above, the ejector is formed in a substantially cylindrical shape and the positions of the refrigerant inflow port, refrigerant outflow port and refrigerant suction port are approximately determined.
For this reason, in the evaporator unit of Patent Document 3, a part of the first evaporator and the second evaporator are arranged on the downstream side (leeward side) in the air flow, the remaining part of the first evaporator is arranged on the upstream side (windward side) of air flow, and a refrigerant pipe for forcibly guiding refrigerant flowing out of the ejector to the first evaporator placed on the windward side is added. Thus, the evaporators are so arranged that the superheat area of the first evaporator and the superheat area of the second evaporator do not overlap with each other as viewed in the direction of air flow.
However, the evaporation temperature of refrigerant in the first evaporator is higher than the evaporation temperature of refrigerant in the second evaporator.
Therefore, when a part of the first evaporator is arranged on the leeward side as in the evaporator unit in Patent Document 3, a temperature difference is produced between air blown out of this part of the first evaporator and air blown out of the second evaporator. As a result, the temperature distribution of air blown out of the evaporator unit cannot be sufficiently suppressed.
As described above, the refrigerant pipe for forcibly guiding refrigerant flowing out of the ejector to the first evaporator is placed on the windward side. This prevents reduction of the size of the evaporator unit. Further, the pressure of refrigerant increased at the diffuser portion of the ejector is lowered due to pressure loss that occurs while the refrigerant passes through the refrigerant pipe. As a result, the cycle efficient (COP) enhancement effect obtained by reducing the consumed power of a compressor cannot be sufficiently obtained.